Apparatus for the removal of a cemented dental structure



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April 16, 1968 BRODIE ETAL 3,377,704

APBARATUS FOR THE REMOVAL OF A CEMENTED DENTAL STRUCTURE Filed Nov. 19,1964 4 Sheets-Sheet l iftifil j/z/vs/v TUFFS 5 5 EQUINE H1175: L./=1 Lnsn F, 7" UFPNEIH April 16, 1968 s. s. BRODIE ETAL 3,377,704

APPARATUS FOR THE REMOVAL OF A CEMENTED DENTAL STRUCTURE Filed Nov. 19,1964 4 Sheets-Sheet 2 April 1 s. s. BRomE ETAL 3,377,704

APPARATUS FOR TEE REMOVAL OF A CEMENTED DENTAL STRUCTURE Filed NOV. 19,1964 4 Sheets-Sheet 3 Pom-4 50 0/36 J\ lmmli A ril 16, 1968 s. s. BRODIEETAL 3,377,704

APPARATUS FOR THE REMOVAL OF A CEMENTED DENTAL STRUCTURE Filed Nbv. 19,1964 ?1 QLEE 4 Sheets-Sheet 4 United States Patent 3,377,704 APPARATUSFOR THE REMOVAL OF A CEMENTED DENTAL STRUCTURE Sidney Steven Brodie, 720Fort Washington Ave., New

York, N.Y. 10040, and Albert de la Lastra, l9 Cambridge Ave., Bethpage,N.Y. 11714 Filed Nov. 19, 1964, Ser. No. 412,540

Claims. (Cl. 32-43) ABSTRACT OF THE DISCLOSURE This invention relates toan apparatus for the removal of a cemented dental structure in which amechanical arrangement capable of transmitting mechanical energy alongthe longiutdinal axis of the structure uses a variety of magneticallyoperable means for imparting impacting forces to the mechanicalarrangement. The magnetically operable means include a controlled sourceof magnetic energy selectively activating movable masses of magneticmaterial to vary the frequency and phase of the impacting sequence.

This invention relates to improvements in dentistry and moreparticularly to improvements in apparatus for the removal of a cementeddental structure.

Dental structures such as bridges and crowns are bonded to natural toothroots by cements. It is well known, that the removal of cemented dentalstructures may be necessary for one or more of the following reasons:

(a) The occurrence of dental decay.

(b) To examine the vitality and pulpal involvement of a prepared tooth.

(c) To repair cemented dental structures made defective by the wear ofmaterials.

(d) The loss of selected supporting teeth.

It is also known that natural tooth roots are connected to bonestructure by a matrix of connecting fibers. The connecting fibersexhibit a resultant vector force which holds the tooth root in place,which vector force operates substantially along a longitudinal axis inthe direction of the top to bottom of the tooth. Thus, properly directedimpacting forces permit the use of high force magnitudes to break thecement bonds holding the dental structure to the tooth root withoutsubstantial detrimental eifect to the fibers or natural tooth roots.

In the prior art, removal of dental structures such as bridges andcrowns was achieved by sacrifice of the tooth, or, by application of arigid grasping means to the structure followed by the manual applicationof an impacting or leverage force in an attempt to break the cementbonds. However, prior art devices could apply only in exact magnitudesof impacting forces since manual means were used. Such manual means werefurther limited in that the oral cavity is not large enough to permiteasy direct impacting to those dental structures located near the rearof the cavity. Other consequences of the use of prior art apparatus arepatient discomfiture, and inconvenience to the dentist occasioned by thecumbersome mechanical apparatus.

It is accordingly an object of this invention to provide a moreefiicient apparatus for the removal of a cemented dental structure.

It is another object of this invention to provide an apparatus for theremoval of a cemented dental structure using precisely regulatedimpacting forces directed along the longitudinal axis of said structure.

It is still another object of this invention to provide an apparatus forthe removal of a cemented dental structure operable in confined regionsof the oral cavity.

3,377,704 Patented Apr. 16, 1968 It is an object of this invention toprovide an automatic apparatus minimizing manual intervention foreifecting the removal of a cemented dental structure.

It is another object of this invention to provide an apparatus for theremoval of a cemented dental structure, which apparatus includes controlmeans remote from the oral cavity.

It is still another object of this invention to provide an electricallyoperable apparatus for the removal of a cemented dental structure.

It is yet another object of this invention to provide an apparatus forthe removal of a cemented dental structure, which apparatus may beselectively coupled to any one of a plurality of permanent bridge orcrown arrangements.

As previously mentioned the direction of application of impacting mustbe translated along the longitudinal axis of the cemented dentalstructure so as to avoid the tearing or twisting of the fiber matrixwhich secures the tooth root to the fiber matrix which secures the toothroot to the bone.

It is accordingly a feature of this invention that the apparatuscomprises means for coupling the structure capable of transmittingmechanical energy along the longitudinal axis of said structure; andmagnetically operable means for imparting forces to the coupling means.

The magnetic actuation of the impacting forces permits the use of a widevariety of electro magnetic control arrangements with the advantage ofprecision and flexibility. The coupling means translates the impactingforces and applies said forces to the cemented dental structures whichavoids injury to the fiber matrix.

It is another feature of this invention that the mecha nism forgenerating the impacting forces comprise at least one movablemagnetically responsive mass operating within a controlled field ofmagnetic energy, the mass being guided to impact upon the coupling meansby selective actuation of the controlled field. Thus, by modulating themagnetic field, it is now possible to control the acceleration anddirection of the mass to achieve selectively varying impactingfrequencies and force magnitudes.

It is another feature of this invention that the mass can be disposedwithin a variety of inductive winding arrangements.

It is a feature of this invention that the means for coupling thecemented dental structure capable of transmitting mechanical energyalong the longitudinal axis of said structure comprise a rigid member,means for grasping the structure, and a pivotably supported leverlinking the rigid member and the grasping means.

It is evident that the impacting of the mass against a portion of therigid member will cause the translation of force through the rigidmember of the grasping means by motion of the pivotably supported lever.

It is accordingly another feature of this invention that the means usedto reposition the mass upon alteration of the magnetic field compriseselective combinations of permanent magnetic and magnetically permeablematerials, or, bistable remanent magnetic materials.

It is another feature of this invention that two movable masses may beused to sequentially impact upon the coupling means. Advantageously,during each impacting cycle two impacts can be delivered in a variety oftimed relations without increasing the frequency of the source.Additionally, rapid successive impacting tends to limit the ability ofthe dental structure to return to its original state.

Restated, the above described arrangements increase the flexibility ofcontrol and frequency of impacting because the motion of one or moremasses causing the impacting is responsive only to an applied magneticfield. Additionally, magnetic means can be used to selectivelyreposition one or more masses.

Other objects, features, and advantages of this invention will becomeapparent from the following description and accompanying drawings inwhich:

FIGURE 1 is a sectional view of one embodiment of the invention.

FIGURE 2 is a simplified diagrammatic illustration of the embodimentshown in FIGURE 1.

FIGURE 3A is another illustration of the embodiment shown in FIGURE 1emphasizing the coupling means.

FIGURE 3B shows an alternative embodiment of the coupling means.

FIGURE 4 shows an alternative embodiment to that shown in FIGURE 3A.

FIGURE 5A shows the use of two movable masses in another embodiment ofthe invention.

FIGURE 5B is a diagrammatic illustration of the embodiment shown inFIGURE 5A.

FIGURE 5C shows the use of two masses in an embodiment alternative tothat shown in FIGURE 5A.

FIGURE 6 shows another embodiment of the invention having two movablemasses with permanent magnetic portions thereof.

FIGURE 7 shows another embodiment of the invention using a single masshaving a permanent magnetic portion thereof.

FIGURE 8 shows another embodiment of the invention using a singlemovable mass formed from bistable remanent magnetic material.

FIGURE 9 illustrates the magnetic interactions of the embodiments shownin FIGURE 8.

In FIGURE 1, the coupling means comprises rigid bar 2 having a hook orgrasping means 1 at one end thereof. The hook or grasping means may beany one of a number of dental implements which can be convenientlyaffixed to firmly grasp a dental crown. The rigid bar is slidablymounted within a movable mass 7. The translation of the bar relative tothe mass is limited by a stop collar 3 fixed to the bar. The mass 7 isformed from any one of a number of magnetically permeable materials suchas soft iron. Surrounding a portion of the bar and the mass is aninductive winding 16. The inductive winding 16 is enclosed within amagnetically permeable casing 9 which supports and completes themagnetic flux path through the movable mass. One end 11 of the movablemass 7 is formed into a conical shape which is intended to nestleagainst a conically shaped indentation of the casing 9. The conicallyshaped indentation is fonmed from a static mass portion. It should benoted, that one end of the rigid bar 2 has a large cross section area 4,the motion of the bar being limited by stop collar 5.

When a magnetic field generated from winding 16 is applied, the fieldintercouples movable mass 7 causing the movable mass to move towardimpact surface 4 of the rigid bar and toward the static mass portion ofcasing 9.

As is illustrated in the figure, the movable mass will first impingeupon the impact surface 4 moving the rigid bar until the mass impingesupon the static mass 10, the stop collars 3 and 5 being so disposed asto permit movement of the bar relative to the static mass until themovable mass closes the air gap between 10 and 11.

In order to reposition the movable mass 7, it is not sufficient tomerely reverse the polarity of the applied magnetic field. This isbecause the movable mass is attracted to the stationary mass It due tothe relative attractive polarity difference; i.e., north-south, orsouth-north. By reversing the polarity of the magnetic field, the sameattractive polarity difference exists. These facts necessitates therepositioning of the movable mass by means other than the varying of thepolarity of the applied magnetic field. Advantageously, therepositioning of the movable mass can be accomplished by use of a springbias 14. The spring 14 causes the movable mass to push against stopcollar 3 thus moving rigid bar 2. The motion of rigid bar 2 is limitedby stop collar 5 impinging upon static mass 10.

FIGURE 2 is a simplified representation of the dy- 4 namics of themovable mass, spring and impact surface 4 of the rigid bar 2 shown inFIGURE 1. When the magnetic field is applied, movable mass 7 translatesto the left against spring bias 14, making initial impact upon surface4- of the rigid bar and continuing to translate to the left until themovable mass is stopped by static mass 10.

In FIGURE 3A the coupling means comprises a pivotable lever 21 couplingthe rigid bar 2 at a first pivot point 23. Additionally, a supportmember 27 is rigidly connected between the casing 9 and a second pivotpin 22. The hook or grasping means 1 is coupled to a third pivot point24. Guiding the u and down motion of hook 1 are guide means 25 and 28afiixed to a support member 27. When a magnetic field is applied tomovable mass 7, said movable mass translates to the left impinging uponsurface 4 of rigid bar 2. This causes lever 21 to rotatecounterclockwise around pivot point 2 2. The rotation of lever 21 pullshook 1 in an upward direction. Similarly, as described in connectionwith FIGURE 1 when the movable mass is repositioned, it pushes againststop collar 3 (see FIGURE 1) causing rigid bar 2 to rotate lever 21 in aclockwise direction. This forces hook I in a down ward direction. Themeasured motion of the hook 1 in actual practice need be only a fewtenths of a millimeter in both the upward or downward direction.

In FIGURE 38 the hook or grasping means 1 is guided in its upward anddownward motion by use of a guide bushing 25 supported by member 28coupled to support member 27 In all of the embodiments, the movable mass7 can be conveniently supported by easing 9. Additionally, the air gapdesign between the movable mass 7 and the stationary mass 8, canoptimize the concentration of flux lines by any one of a number of wellknown configurations. This fact is illustrated conveniently in FIGURE 1by the conica'lly shaped air gap.

Self-evidently, movable mass 7 can impact upon the rigid bar 2 in eithera compressive or tensional sense.

FIGURE 4 shows the movable mass 7 applied in a compressive sense againstrigid bar 2. In this embodiment, the rigid bar is connected to the leverat pivot point 23, while two support members 27a and 27b are used.Support member 2712 is coupled to pivot point 22, while support member27a positions the guide bushing 25.

In FIGURE 5A two movable masses 7a and 7b are shown slidably mountedupon rigid bar 2. Two independent inductive windings 16a and 1611 areused. The magnetic flux path generated by windings 16a substantiallycouples mass 7a through casing 9 and static mass 10. Similarly, the mainflux path including movable mass 7b comprises the entire extent ofcasing 9, static mass 10, and movable mass 7a. The windings 16a and 1611are electrically connected to phase control means 50. Operatively,windings 16a are actuated first. This causes movable mass 7a to impingeupon member do. After the field has been iemoved from windings 16a, afield is applied through windings 16b causing mass 7b to impinge uponelement 4b. The magnetic field strength emanating from windings 16b canbe used to maintain both masses in contact relation with each other andwith static mass 10. Repositioning means, not shown, are used in asimilar arrangement as that shown in FIGURE 1. Advantageously, theexcitation of windings 16a and 1611 can be made in differentpredetermined patterns with respect to time to achieve a wide variety ofrhythmic variations.

FIGURE 5B is a simplified schematic of the relations between movablemass 711 and 7b together with rigid bar 2.

FIGURE 5C is an embodiment showing two movable masses 7a and 7bimpacting upon rigid bar 2 in compressive relation. In this embodimentmovable mass 7b is slidably mounted upon rigid bar 2, while movable mass7a impacts directly upon element 4a.

As previously mentioned, each movable magnetically permeable mass mustoperate against a spring bias, or, more generically a restoring force.Advantageously, the

use of permanent magnetic material or bistable remanent magneticmaterial may provide a restoring force to replace the spring bias.

FIGURE 6 shows two movable magnetic masses 7a and 7b slidably mounted onrigid bar 2. Each movable mass is formed from a portion of permanentmagnetic material such as Alnico and a magnetically permeable portionformed from soft iron. Additionally, the static mass is formed from thesame permanent magnetic material such as Alnico. All the permanentmagnetic material exhibits the same magnetic polarity. Furthermore, thepermanent magnetic material forms the outer face of static mass 10 andis disposed opposite the permanent magnetic face of movable mass 7a.

The magnetic field emanating from winding 16a is of sufiicient magnitudeto overcome the repulsive magnetic fields existing between the permanentmagnetic faces on the static mass 10 and the movable mass 7a. A somewhatlarger field (due to the longer flux path) is necessary to move mass 7btowards mass 10. When the applied magnetic fields are reduced, therepulsive fields existing between the permanent magnetic faces willcause the masses 7a and 7b to be repositioned. This may be seen moreclearly in FIGURE 7.

In FIGURE 7 a single mass is shown with the air gap ends 9a and 9b ofthe casing extending over the magnetically permeable portions of themovable mass 7. In this embodiment, as in the embodiment shown in FIG-URE 6, the applied magnetic field must be of sufiicient intensity toovercome the repelling field between the oppositely disposed permanentmagnetic faces of the static mass 10 and the movable mass 7.

FIGURE 8 shows an embodiment identical with that shown in FIGURE 7except that the movable mass 7 is formed from bistable remanent magneticmaterial and the static mass 10 is formed from magnetically permeablematerial. Any one of a number of well known ferrites havingsubstantially square hysteresis loops may be used for the bistableremanent material.

The operation of the embodiment in FIGURE 8 may be understood by alsoconsidering FIGURE 9. It should be recalled that square loop materialexhibits two magnetic states. The material may be driven into a firststable state by the application of magnetic field of a first polarityand into a second stable state by the application of a magnetic field ofopposite polarity.

FIGURE 9A shows that when mass 7 is in a first stable state, the appliedfield through static mass 10 is in a series aiding direction. Thiscauses mass 7 to move towards the static mass 10. When the appliedmagnetic field is removed, as is shown in FIGURE 9B, the masses areattractively connected.

It is well known, that there is a phase lag in driving remanent magneticmaterial from a first into a second stable state and vis-a-vis. As aconsequence when a magnetic field of opposite polarity is applied, arepulsive force exists between the two masses separating mass 7 frommass 10. This is because the movable mass 7 has not changed state whilean opposite polarity has been induced in the static mass 10. With thecontinued application of the oppositely poled magnetic field, mass 7 isdriven into a second stable state and is series aiding with respect tothe flux in static mass 10. This causes mass 7 to move toward the staticmass. These interactions are shown in FIGURES 9C and 9D respectively.Consequently, sensitive frequency control may be obtained through theuse of bipolar current pulses applied to windings 16.

It is understood that there are numerous arrangements for affixing ahook or other grasping implement to the crown or other cemented dentalstructure and various changes in the details, arrangements of parts,which have herein been described may be made by those skilled in the artwithout departing from the principle and scope of the invention.

What is claimed is:

1. An apparatus -for the removal of a cemented dental structurecomprising:

means for coupling the structure capable of transmitting mechanicalenergy along the longitudinal axis of said structure;

a first and a second movable magnetically permeable mass;

means for guiding the first and second mass to impact upon the couplingmeans;

a controlled source of magnetic energy for selectively generatingmagnetic fields intercoupling the masses and for accelerating the massestoward the coupling means, the controlled source including phase controlmeans for regulating the magnetic fields such that the first mass isaccelerated independent 01 the second mass; and

means for repositioning the masses along the guide means upon alterationof both fields.

2. An apparatus for the removal of a cemented dental structurecomprising:

means for coupling the structure capable or transmitting mechanicalenergy along the longitudinal axis of said structure;

a first and second movable mass each having a magnetically permeableportion and a permanent mag netic portion, the permanent magneticportions being of the same polarity;

means for guiding the masses to impact upon the coupling means; and

means for impressing a magnetic field of sutficient intensity toaccelerate the masses "toward the coupling means;

the permanent magnetic portions of each mass being of sufiicientintensity to reposition the masses along the guide means upon removal ofthe magnetic field.

3. An apparatus for the removal of a cemented dental structurecomprising:

means for coupling the structure capable of transmitting mechanicalenergy along the longitudinal axis of said structure;

a movable mass having a magnetically permeable portion and a permanentmagnetic portion thereof;

means for guiding the mass to impact upon the coupling means;

magnetically permeable means magnetically linking the mass and having aportion of its extent formed from permanent magnetic material disposednear the mass;

means for impressing a magnetic field to accelerate the mass in a firstdirection along the guide means;

the permanent magnetic portions emanating fields of sufficient intensityto accelerate the mass in a second direction along the guide means uponthe removal of the magnetic field.

4. An apparatus for the removal of a cemented dental structurecomprising:

means for coupling the structure capable of transmitting mechanicalenergy along the longitudinal axis of said structure;

a movable mass formed from bistable remanent magnetic material;

means for guiding the mass to impact upon the coupling means;

magnetically permeable means magnetically linking the mass having aportion of its extent formed from permanent magnetic material;

means for inducing a first stable state in the bistable magnetic massaccelerating the mass in a first direction along the guide means; and

means for inducing a second stable state in the bistable magnetic massfor accelerating the mass in an opposite direction.

7 5. An apparatus according to claim 4, characterized in that:

the means for establishing the first and second stable states comprisinga winding surrounding the mass; and a source of bipolar current pulsescoupled to the winding arrangement.

References Cited UNITED STATES PATENTS 8 2,628,319 2/1953 Vang 3l0-152,640,266 6/ 1953 Sarti 32-43 2,777,198 1/1957 Wallace 32-61 3,129,3474/1964 TOgnOla 31015 FOREIGN PATENTS 316,478 8/ 1929 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

10 J. W. HINEY, Assistant Examiner.

